1. Field of the Invention
This invention relates to a low friction seal between relatively moving parts particularly where there is a considerable pressure differential across such seal.
2. Prior Art
Zones of high pressure differential, particularly in gas turbine engines often require an effective gas seal to maintain such differential. This requirement has posed a challenge where a gas seal has been required between a moving part and a stationery part. For example, attempts have been made to provide a gas seal in an exhaust nozzle of a gas turbine engine between convergent and divergent flaps and the engine wall adjacent thereto. This is because on the inside of such flaps are hot core gasses at, e.g., 3,000.degree. F. and 80 psi while on the outside of such flaps, is cooling air at, eg. 600.degree. F. and 88 psi.
Prior art gas seals employed for sealing a moving part to a static part, e.g. a wall, have employed sliding metal-on-metal parts which have high friction, high wear rates and high leakage. The stiffness of the these seals prevent them from adjusting to surface irregularities and small deflections. Hence the high leakage.
An example of the above prior art gas friction seal is shown in FIG. 1 wherein convergent or divergent flap 10 (of a gas turbine engine) moving in proximity with housing wall 12, employs a metal strip seal 14, which slides or skids in friction contact with the wall 12. As noted above, such prior art seal is subject to high friction, wear and leakage.
Other attempts have been made to provide a gas seal between moving and stationary parts in the prior art. See for examples, U.S. Pat. No. 5,014,917 to Sirocky et al (1991). This reference discloses, per FIG. 1, a seal element 10 which is a friction seal in sliding engagement with a side wall, which can cause wear and abrasion of the seal element and/or side wall and consequent leakage problems therebetween. Accordingly there is a need and market for a gas seal between moving and stationary parts or surfaces, that obviates the above prior art shortcomings.
There has now been discovered a gas seal between moving and stationary parts or surfaces that is effective in high temperature, large delta pressure environments.